Clamped photoconductive unit for electrophotography

ABSTRACT

A PHOTOCONDUCTIVE MEMBER CARRYING A BROAD CLAMP PREASSEMBLED IN PERMANENT NONFRACTURING ELECTRICAL CONTACT WITH AN EXTREMELY THIN CONDUCTIVE LAYER OF SUCH MEMBER AND PROVIDING AN ELECTRICAL AND MECHANICAL COUPLING BETWEEN THE CONDUCTIVE LAYER AND ELECTROPHOTOGRAPHIC APPARATUS. THE CLAMP MAY CONTAIN MOUNTING PERFORATIONS TO FACILITATE PHYSICAL ATTACHEMENT TO SUCH APPARATUS.

Jan. 5, 1971 H. T. HODGES 3,552,957

CLAMPED PHOTOCONDUCTIVE UNIT FOR ELECTROPHOTOGRAPHY HOWARD T. HODGES INVENTOR.

ATTORNEYS H. T. HODGES 3,552,957

CLAMPED PHOTOCONDUCTIVE UNIT FOR ELECTROPHOTOGRAPHY Jan, 5, 1971 2 Sheets-Sheet 2 Filed March 6, 1967 HOWARD T. HODGES gg; {MW

INVENTOR ATTORNEYS United States Patent CLAMPED PHOTOCONDUCTIVE UNIT FOR ELECTROPHOTOGRAPHY Howard T. Hodges, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey Filed Mar. 6, 1967, Ser. No. 620,906 Int. Cl. G03g 5/00 U.S. Cl. 96-15 11 Claims ABSTRACT OF THE DISCLOSURE A photoconductive member carrying a broad clamp preassembled in permanent nonfracturing electrical contact with an extremely thin conductive layer of such member and providing an electrical and mechanical coupling between the conductive layer and electrophotographic apparatus. The clamp may contain mounting perforations to facilitate physical attachment to such apparatus.

This abstract is required by U.S. Patent Oflice Rules. For a definition of the invention, reference should be made to the claims in view of the following disclosure.

This invention deals with apparatus for electrophotographic processes having a photosensitive member with at least two layers, an electrophotosensitive layer and a conductive layer. The member may also contain other layers, for example, support layers, protective surface layers, barrier layers and/or masking layers. This invention has particular application to photosensitive members which are re-usable, flexible, transparent sheets.

A number of electrophotographic processes and apparatus have been suggested in which a photoconductive member is exposed through a transparent conductive layer; see, for example, U.S. 2,825,814, Walkup; U.S. 2,986,535, Gundlach; U.S. 2,676,100, Huebner; U.S. 2,866,903, Berchtold; U.S.3,256,089, Clark et al.; and U.S. 2,277,013 Carlson. In most of these, transparency of a support and/ or a photoconductive layer are required in addition to transparency of the conductive layer. Such processes and apparatus have not found substantial commercial use compared to those using opaque conductive layers. This is true despite the appearance in recent literature of a large number of good transparent photoconductors readily coated on known strong transparent supports; see U.S. 3,141,770, Davis and Fr. 1,383,461.

A significant reason for this lack of commercial application of transparent photoconductive members resides in the fact that transparency of the conductive layer greatly increases the problem of electrically connecting it to other parts of the apparatus. This problem is due to the fact that transparency in the most useful types of conductive layers is generally considered to be obtainable only with extreme thinness of such layers. In the case of a large number of metals, good transparency is obtained only at thicknesses of .02 micron. Certain metallic salts, such as cuprous iodide, are conductive enough for much electrophotographic work and are transparent in somewhat greater thicknesses. Nevertheless, even with the best materials, it is common for those practicing electrophotography with transparent conductors to be faced with the problem of electrically contacting a layer in the neighborhood of 0.1 micron thick.

If the photoconductive member having a transparent conductive layer could be factory installed in a machine and not require field replacement, certain prior art clamping mechanisms designed for opaque materials might be practical; see, for example, U.S. 2,277,013, Carlson and U.S. 2,583,546, Carlson. However, modern commercial 3,552,957- Patented Jan. 5, 1971 applications of electrophotography require occasional field replacement of the photoconductive member. Thus, for such a commercial application of transparent conductive layers in electrophotography, a more reliable and more simply applied mechanism is essential.

It is an object of this invention to provide means for establishing reliable electrical contact between part of an electrophotographic apparatus and an extremely thin conductive layer of a periodically replaceable photoconductive member used in said apparatus.

It is another object of this invention to provide means for establishing such contact although the conductive layer is thin enough to be transparent and is part of a flexible photoconductive sheet.

It is another object of this invention to facilitate establishing such contact upon replacement of the photocontive member in the electrophotographic apparatus by an unskilled operator.

It is another object of this invention to make electrical contact with a thin transparent conductive layer of a flexible replaceable photoconductive sheet while increasing the rigidity of the sheet and improving its ease in handling and mounting.

It is another object of this invention to provide means for establishing electrical contact between the thin conductive layer of a photoconductive sheet and ground, a voltage source or other apparatus.

It is another object of this invention to provide means for ensuring the aforementioned contact with a thin conductive layer of a flexible photoconductive sheet while providing with the same structure means for easy mounting of the sheet onto an apparatus.

Pursuant to the invention, these and other objects are accomplished by a novel clamped photoconductive unit. A clamp contacts the conductive layer over a broad enough area to give good electrical continuity without dependence on fracturing of the layer. At the same time, it is sufliciently lightweight to be carried by the photoconductive member. Accordingly, the clamp can be reliably and permanently attached to the photoconductive member in the factory. With the clamp as part of the photoconductive unit, it is easily connected to the electrophotographic apparatus in the field.

The invention has special application to flexible photoconductive sheets because the clamping arrangement can add rigidity to the sheet and insure its proper alignment in electrophotographic apparatus even though the sheet is installed in the apparatus by an unskilled operator. According to this feature of the invention, the clamp itself can contain mounting-pin perforations or other means for attaching the unit to a drum or other carrier or mount.

In the drawings:

FIGS. 1, 2, 3, and 4 are greatly enlarged cross sections illustrating clamped photoconductive units according to this invention.

FIGS. 5, 6, 7, and 8 are perspective views of various embodiments of the invention.

FIGS. 9, 10, 11, and 12 are perspective views illustrating structures for mounting the photoconductive units in electrophotographic equipment.

Referring to FIGS. 1 through 4, a support 10 has at least two extremely thin layers coated thereon, a photoconductive layer 13 and a conductive layer 11, together forming a photoconductive member. As mentioned above, protective, masking, barrier and/or other layers also can be coated on the support.

According to the invention an area 14 of the conductive layer 11 is exposed, i.e., not covered by the photoconductive layer 13. Permanent mechanical and electrical contact are made with this fragile conducting layer 11 by gripping the layer 11 and the support 10 between two portions 15 and 16 of a clamp. As illustrated in FIG. 1, portion 15 of the clamp touching the conducting layer 11 comprises a conducting plate, while the other portion 16 touching the support layer may be either conducting or insulating. According to FIG. 1, these two portions 15 and 16 are urged toward each other by one or more rivets or other fastening means 17.

As shown in FIG. 2, support is formed of flexible film. Upper and lower clamp portions 21 and 22 may consist of a single sheet of metal, preferably spring metal, folded over to clamp the support and the exposed area 14 of the conductive layer 11. That is, the upper plate portion 21 and the lower portion 22 are made from a single sheet and the clamping pressure is provided by the material itself folded and forced into clamping relation.

Two other features are shown in FIG. 2. The upper plate 21 extends not only over the exposed area 14 of the conductive layer 11 but also overlaps an area 23 of the photoconductor. Clamp 21 overlaps both the area 14 of the conductive layer 11 and the area 23 and applies pressure to both. A second feature shown in FIG. 2 is a lug 24, which may be formed from the lower portion 22 and extends into the flexible support 10 to clamp it tightly and to keep it from slipping between the clamp portions 21 and 22. In many applications of the invention lug 24 will not be necessary since in general the clamp portions 21 and 22 hold the film very tightly.

FIG. 3 illustrates an embodiment of the invention in which the exposed area 14 of the conductive layer 11 does not extend to the edge of the support 10. In this particular embodiment, a lower clamp portion 51 is shown as being formed of insulating material and secured to the upper conducting clamp portion by a rivet 52. Although an area of the photoconductor 13 is shown along the edge of the conductive layer 11, the total thicknesses of the layers 11 and 13 is very small and their compression between the clamp members 15 and 51 is such that layer 11 is pressed against the clamp portion 15, in spite of the presence of the photoconductor, both to the left and the right of the area of contact. In fact, the presence of other thin layers between, on top of or below the photoconductor and the conductive layers similarly do not interfere with the invention, as illustrated by the presence of a barrier layer 12 between the conductive layer 11 and the photoconductive layer 13.

Certain prior art mechanisms used with much thicker conductive layers used rough, jagged or piercing surfaces on top of the photoconductor to fracture or puncture part of the material and establish contact with the conductive layer. With an extremely thin layer, for example one thin enough to be transparent, such means does not effectively make contact, because the total area of conductive engagement is too small for any reasonable size of such clamp. Although an occasional fracturing of the conductive surface will not destroy useful contact, the contact as shown, occurs between the surface of the conductive layer and a broad, smooth surface of the clamp and involves no substantial fracturing of the conductive layer.

Clamping structures as described above in accordance with the invention have been found to provide good contact with extremely thin conductive layers that are mounted on the surfaces of supports. In actual experience, the components thus mounted provide the necessary electrical contact with elements of electrophotographic apparatu and cannot be easily damaged by improper usage. Although for many applications it is not necessary to use any conductive paint, glue, paste or other soft conductive material between the clamp and the conductive layers, on some occasions there is an advantage in using such materials. Such soft conductive layer helps achieve no fracturing contact between the clamp and an unsmooth plate. Use of such a soft conductive material is shown in FIG. 4 at 9. Use of the clamped photoconductive unit applied in the factory according to the invention allows application of any such intermediate-material more readily and under more controlled conditions than if it had to be applied in the field.

There are several satisfactory ways of exposing an area of the conductive layer for contact With the clamp. One such method is to apply the photoconductive and other surface layers from a coating means (hopper, roll, etc.) somewhat narrower than the sheet being coated so that none of the coating is applied to the edge strips of the conductive layer. Similarly, the coating can be applied through a stencil that covers Where no coating is desired. Alternatively, such coatings can be removed where desired, with solvent which does not dissolve the conductive layer or the support.

An important feature of this invention is the convenience provided by the clamps for alignment in and attachrnent to electrophotographic apparatus. In FIG. 1 perforations shown by broken lines 18 and 19 arearranged to fit over pins, preferably spring urged pins, in an electrophotographic copier. The pins and perforations are so arranged that the photoconductive sheet is in proper alignment in the machine when the pins engage these perforations. If the bottom portion 16 is formed of metal and rests on a conductive drum, electrical connection of layer 11 to the drum is assured through the rivets 17. However, if the plate 16 is formed of insulating material and contact is to be made through the pins on the copier, it is sometimes better to have the perforations 18 on the plate 15 slightly smaller than the diameter of the perforations on the portion 16 and the support 10. This slight clearance assures that the pins engage the conductive plate 15.

Other perspective views of the clamps are shown in FIGS. 5 through 8 with emphasis on the means for attaching them to an electrophotographic printer. In each case the clamp portions are sufficiently lightweight, and are factory attached to the photoconductive member, so that they can be carried by that member, together forming a unitary clamped photoconductive unit. The difficulties of electrical contact between the clamp and the thin layer are surmounted in the factory, thereby insuring excellent electrical contact when the unit is installed in a machine.

In the embodiment shown in FIG. 6 the conductive upper plate 31 is riveted as at 32 to a lower plate 33, which extends considerably beyond the edge 36 of the support 10. The perforations 34 are solely in the lower plate 33. In this embodiment the clamp and edge 36 of the support can be of the same length. With this embodiment, a succession of clamped photoconductive units can be mounted with the trailing edge of one unit and the leading edge of the next unit both mounted on the same row of pins.

FIG. 7 corresponds to FIG. 2 and illustrates a further feature in which clamp 21 has upper and lower portions, the lower portion extending beyond the sides of the support 10, as shown at 22, with the perforations 26 located in this extension. FIG. 8 shows another embodiment using a wrap-around or a folded clamp 40. In this case, lugs 42, which are bendable, replace rivets 17 and 52. The mounting perforations 43 are in the portion of clamp 40 lying outside the margin of support 10.

In FIG. 9 clamp members and 61 are curved. They clamp the support 10 and its thin conductive layer and hold them tightly by means of rivets 62. The curvature of the clamp permits its easy mounting on a rod 63, which is spring urged to supply torque, as shown by arrow 64, stretching the photoconductive sheet by pins 65 pressing against the sides of the perforations.

FIGS. 10, 11 and 12 show a mounting of the photoconductive unit in various electrophotographic copiers. In FIG. 10, a flexible photoconductive sheet is held taut so that it normally lies fiat, for example, during exposure of the sheet in the machine. A chain drive carrying a clamp 71 moves the photoconductive unit through the various stations of the electrophotographic copier. With each clamp 71 is a fixed rod 72 carrying thereon a cylindrical sleeve, which is partly rotatable on the rod 72. As indicated by arrows 73, successive sleeves 75 are urged in opposite directions (clockwise and counterclockwise), by springs 74 engaging respective pins on the rods and sleeves. In practice it is sufiicient for one sleeve to be fixed on its associated rod and for the other sleeve to be rotatable and spring urged.

Two slightly different types of photoconductor units are shown in FIG. 10. One sheet 101 has a respective curved clamp portion 76 on each end of the sheet, i.e., along the leading and trailing edges. These clamp portions 76 are held together by rivets 77 and include perforations which fit over pins 78 in sleeves 75. The spring urged rotation of the sleeves 75 engaging the two ends of the sheet, tends to stretch the sheet and hold it fiat. The second unit 102 is the same as the first except that it has the metal clamps only at one edge of the sheet and merely has perforations 81 in the sheet itself to extend over the pins 78. According to the invention, the clamp on either or both ends of the sheet is used for mounting the unit on a carrier shown in FIG. 10.

In FIG. 11, the sheet is wrapped around a section of a carrier comprising a drum 89. In this arrangement, drum 89 has a longitudinal V-groove 85 in its periphery, and a series of pins 82 are located along each side of the groove. Clamps 15 and 16, corresponding to FIGS. 1 and 2, contain perforations which fit over pins 82, one series of which can be spring urged toward the center of the drum or the bottom of the groove. A brush 83 engages the upper plate 16 of the clamp to maintain electrical contact between the photoconductor unit and the machine.

FIG. 12 is an embodiment which has clamp portions 15 and 16 as hereinabove described at one end of the sheet, with perforations 18 to fit over fixed pins 95 that are mounted in bars 72. The other end of the sheet includes, between a pair of clamps 91 and 92, a resilient metal sheet or Web 19, which acts as an extension of the clamp. The outer end of a resilient conductor sheet 90 has perforations or a pair of clamping plates 93 and 94, also with perforations to fit over the pins 95 on which is mounted the leading edge of a next photoconductor unit. If electrical contact between the photoconductor units and the machine is obtained through the pins 95, sheet 90 need not be conductive. More reliable electrical contact, however, is obtained if the sheets 90 are formed of conducting material. The resiliency of the sheet or web 90 holds the sheets taut and may also help prevent xerographic toner from passing through gaps between units. Extra cross bars may be included with the sheet laid across them to hold the photoconductive surface 13 slightly higher than the end clamps for convenience in toning.

Although the invention is useful with any extremely thin conductive layer, the invention is most important when using transparent conductive layers. Examples of such conductive layers and their thicknesses can be found in US. 3,245,833, Trevoy. When exceptional transparency is critical to the process and when nonmetallic conductors are used, such thicknesses commonly are in the neighborhood of 0.1 microns. Other less dense materials can be somewhat thicker than 0.1 microns and still be at least partially transparent and partially conductive and therefore useful in some electrophotographic processes.

Although the invention has been described with reference to certain preferred embodiments, it will be understood that variations and modifications can be effected without departing from the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

I claim:

1. An electrophotosensitive unit for use in an electrographic apparatus of the type having an electrical terminal and having a carrier that is adapted to move between electrophotographic stations, said unit comprising:

(a) a layered member including (1) asupport layer,

(2) a photoconductive layer,

(3) a thin electrically conductive layer positioned between said support layer and said photoconductive layer, an area of the surface of said conductive layer opposite the support layer being exposed, and

(b) clamp means preassembled on said layered member and adapted to be mounted on said carrier and connected to said terminal, said clamp means havmg (1) an electrically conductive plate portion overlying said exposed area of the conductive layer,

(2) a second portion overlying said support layer opposite said conductive plate portion,

(3) means urging said portions toward each other establishing electric contact between the conductive layer and the conductive plate portion and permanently attaching said clamp means to the layered member.

2. A photoconductive unit for insertion into electrophotographic apparatus of the type having an electrical terminal, said unit comprising (A) a photoconductive member including (1) a support layer,

(2) a photoconductive layer,

( 3) a thin electrically conductive layer positioned between said support and photoconductive layers, an area of the conductive layer surface opposite the support layer being exposed, and

(B) clamp means permanently attached to and carried by said photoconductive member and adapted to be electrically connected to said electrical terminal and having 1) an electrically conductive plate portion having a surface overlying said exposed area of the conductive layer,

(2) a second portion overlying said support layer substantially opposite said conductive plate portion, and

( 3) means urging said portions toward each other to establish electrical contact between the conductive layer and the conductive plate portion.

3. A photoconductive unit usable in an electrophotographic printer comprising ,(A) a photoconductive sheet including (1) a flexible transparent support layer,

(2) a photoconductive layer,

(3) a thin transparent electrically conductive layer positioned between said support and photoconductive layers, an area of the surface of said conductive layer opposite the support layer being exposed along at least one edge of said sheet, and

(B) a clamp means permanently attached to and carried on said photoconductive sheet having (1) an electrically conductive plate portion, a surface thereof overlying said exposed area of the conductive layer,

(2) a second portion positioned below said support layer substantially opposite said conductive plate portion,

(3) means permanently urging said portions toward each other to establish electrical contact between the conductive layer and the conductive plate portion.

4. A unitary element for electrophotographic apparatus comprising (A) a photoconductive sheet including 1) a flexible transparent support layer,

(2) a photoconductive layer,

(3) a thin transparent electrically conductive layer (2) a second portion lying along said support layer substantially opposite said conductive plate portion, and

(3) means urging said portions toward each other to establish electrical contact between the conductive layer and the conductive plate portion.

5. A photoconductive unit according to claim 4 wherein at least one of said plate portions has a means for mounting the photoconductive unit into an electrophotographic apparatus.

6. A photoconductive unit according to claim 4 wherein at least one of said plate portions has a plurality of mounting perforations.

7. A photoconductive unit according to claim 4 Wherein said plate portions comprise metal plates and said urging means comprises at least one rivet extending through the support layer.

8. A photoconductive unit according to claim 4 wherein said plate portions and urging means consist of a single sheet of metal folded over an edge of the support.

9. A photoconductive unit usable in an electrophotographic printer comprising (a) a photoconductive sheet including (1) a flexible transparent support layer,

(2) a photoconductive layer,

(3) a thin transparent electrically conductive layer positioned between said support and photoconductive layers, an area of the surface of said conductive layer opposite the support layer being exposed along at least one edge of said sheet, and

(b) clamp means supported by and attached to said photoconductive sheet as an integral portion thereof and running at least the full length of said edge thereby adding rigidity to said sheet, said clamp means having (1) an electrically conductive plate portion having a smooth surface overlying said exposed area of the conductive layer,

(2) a second portion overlying said support layer opposite said conductive plate portion,

(3) means urging said portions toward each other to establish electrical contact between the conductive layer and the conductive plate portion.

10. A photoconductive unit usable in an electrophotographic printer comprising (a) a photoconductive sheet including 1) a flexible transparent support layer,

(2) a photoconductive layer,

(3) a thin transparent electrically conductive layer positioned between said support and photoconductive layers, an area of the surface of said conductive layer opposite the support layer being exposed, and

(b) a clamp means carried on said photoconductive sheet as an integral portion thereof and having (1) an electrically conductive plate portion, a smooth surface thereof overlying said exposed area of the conductive layer,

(2) a second portion positioned below said support layer substantially opposite saidconductive layer plate portion,

(3) means urging said portions toward each other to establish electrical contact between the conductive layer and the conductive plate portion,

(4) means for mounting said unit in said electrophotographic printer.

11. A photoconductive unit for insertion as a compo-- nent part in an electrophotographic apparatus, said apparatus being of the type having a carrier for positioning a photoconductive layered member in electrophotographically operative position in said apparatus, said carrier including electrically conductive mounting pins electrically connected to an electrical ground, said unit comprising (a) a photoconductive sheet including (1) a flexible transparent support layer,

(2) a photoconductive layer,

(3) a thin transparent electrically conductive layer positioned between said support and photoconductive layers, an area of the surface of said conductive layer opposite said support layer being exposed along at least one edge of said sheet, and

(b) clamp means carried as an integral assembly by said photoconductive sheet and running at least the full length of said edge thereby adding rigidity to said sheet, said clamp means having (1) an electrically conductive plate portion having a surface overlying said exposed area of the conductive layer, said surface being smooth enough that if pressed against said conductive layer it will not substantially fracture it,

(2) a second portion opposite said conductive plate portion,

(3) means urging said portions toward each other to establish electrical and physical contact between the conductive layer and the conductive plate portion,

(4) perforations in said electrically conductive plate portion adapted for mounting and electrical cooperation with said mounting pins whereby said unit may be readily inserted in said electrophotographic apparatus and electrical continuity readily obtained therebetween.

11/1967 Robillard 96-1.5 5/1969 Bean et al 96l.5X

GEORGE F. LESMES, Primary Examiner M. B. WITTENBERG, Assistant Examiner U .5. Cl. X.R. 355-3 

